This is a really small alarm that could easily fit inside a pocket. However, I also demanded reliable operation, simple construction and very low power consumption. I started with CMOS logic gates, but was soon forced to abandon the concept after a few unsuccessful (and far too complicated) takes. Then I suddenly realized that a [...]
This battery charger is for 12V Seales Lead Acid (SLA) battery. It is actually a half-wave rectifier. It only charges the battery on every half cycle. The plug pack doesn’t like this as it leaves residual flux in the core of the transformer and causes it to overheat. There are a number of points we [...]
Introduction: Amplifier device that accepts a varying input signal and produces an output signal that varies in the same way as the input but has larger amplitude. The input signal may be a current, a voltage, a mechanical motion, or any other signal; the output signal is usually of the same nature. The most common [...]
Here is a simple circuit based on two transistors that can be used to control the speed of a 12 V DC fan depending on the temperature.A thermistor (R1) is used to sense the temperature. When the temperature increases the base current of Q1 (BC 547) increases which in turn decreases the collector voltage of [...]
Rain alarm is a simple circuit using water sensor (transducer) that produces an audible alarm whenever rain falls. The circuit can be based on two transistors and or a NE555 IC. The two transistors are wired as a switch which goes on when the base of Q1 is shorted to the positive of the supply [...]
This Batteries Charger is intended for charging sealed lead-acid batteries with a solar panel in small and portable applications. The customary diode that prevents the battery from discharging through the solar panel has been replaced by a FET-comparator combination. The batteries charger will stop charging once a pre-set voltage (temperature compensated) has been reached, and [...]
This camera battery charger circuit will keep the battery for a train mounted camera charged and will shut the camera off after a few seconds when power is no longer applied to the track. This camera battery charger circuit is designed for DCC systems and the battery is essentially used as a capacitor as it [...]
